set_test.go

package main

import (
	"strconv"
	"testing"
)

func BenchmarkSetSpeed(b *testing.B) {
	set := make(map[string]int)
	for i := 0; i < 10; i++ {
		set[strconv.Itoa(i)] = i
	}

	b.Run("explicit index", func(b *testing.B) {
		for i := 0; i < b.N; i++ {
			s := make([]string, len(set))
			j := 0
			for k := range set {
				s[j] = k
				j++
			}
			SS = s
		}
	})

	b.Run("append len=0 cap=len(set)", func(b *testing.B) {
		for i := 0; i < b.N; i++ {
			s := make([]string, 0, len(set))
			for k := range set {
				s = append(s, k)
			}
			SS = s
		}
	})

	b.Run("append len=0 without cap", func(b *testing.B) {
		for i := 0; i < b.N; i++ {
			var s []string
			for k := range set {
				s = append(s, k)
			}
			SS = s
		}
	})
}

$ go test -run=XXX -bench=BenchmarkSetSpeed -benchmem -benchtime=10000000x
goos: darwin
goarch: amd64
pkg: github.com/inkel/misc-go-benchmarks
cpu: Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
BenchmarkSetSpeed/explicit_index-12         	10000000	      177.5 ns/op	    160 B/op	      1 allocs/op
BenchmarkSetSpeed/append_len=0_cap=len(set)-12         	10000000	      180.5 ns/op	    160 B/op	      1 allocs/op
BenchmarkSetSpeed/append_len=0_without_cap-12          	10000000	      427.7 ns/op	    496 B/op	      5 allocs/op
PASS
ok  	github.com/inkel/misc-go-benchmarks	8.371s